Rotatable Cutting Tool

ABSTRACT

A rotatable cutting tool with a shank for locating the rotatable cutting tool on a work face, a body and a hard tip wherein said body is of a generally tapered shape and has at least one flight wherein said at least one flight extends longitudinally and at least partially around the body whereby movement of the rotatable cutting tool through a substrate urges the tool to rotate.

FIELD OF THE INVENTION

The present invention relates to a rotatable cutting tool for boring andsimilar operations. The cutting tool is for insertion into a tool holderassembly that allows the cutting tool to rotate within the tool holderassembly. Typically, the tool holder assembly is mounted on a drivenwork face, such as a cutting head, a drum, a chain, or the like.

BACKGROUND OF THE INVENTION

Rotatable cutting tools have found a variety of uses in applications inwhich the cutting tool is used to impact on or grind away a surface. Oneexample of the use of rotatable cutting tools is as a component of aroad planing tool in a road planing machine. Typically, road planingmachines include a drum with blocks mounted on the drum to retain therotatable cutting tools. The blocks are generally formed with a centralbore for receiving the rotatable cutting tools. The rotatable cuttingtools generally comprise an elongate steel body with a hard cementedcarbide tip that has been mounted into a socket contained in the distalend of the steel body. The steel body includes a shank at the proximalend for insertion into the bore of the block. The shank permits rotationof the rotatable cutting tool within the bore in the block. In use, thedrum rotates and the rotatable cutting tools impact on and grind awaythe road surface.

The tip is generally formed separately from the body of the rotatablecutting tool and mounted in an insert at the distal end of the body ofthe rotatable cutting tool.

Rotatable cutting tools are subjected to extreme forces as well as tosevere wear conditions in use. Such extreme forces and severe wearconditions can quickly abrade the cutting tool. In order to maximise theusable life of a cutting tool, the cutting tool is permitted to rotatewithin the tool holder so that the wear is distributed around thecutting tool and not concentrated on any particular side of the tool.

It is desirable to ensure consistent rotation of the cutting tool withinthe holder during operation. The cutting tool is rotated by the impactof the tool on the surface. Examples of tips used in cutting toolsinclude conical tips, dome shaped tips and compound tips where a cone ordome extends from a cylindrical shaft. Such tips are generallyrotationally symmetrical. In order to facilitate rotation, profiled tipshave been employed. Examples of profiled tips include multifaceted tipssuch as tips having a pyramid shape.

The rotation of the cutting tool within the holder can be impaired bydebris working its way between the cutting tool and the tool holder.Impaired rotation of the cutting tool, or in the complete failure of thecutting tool to rotate results in the severe uneven wear of the hard tipand can possibly result in the displacement of the tip from the body ofthe cutting tool.

The cutting tools are attached to a driven member such as, for example,a chain, a wheel, or a drum. Typical applications for rotatable cuttingtools include mining, ditching, trenching, drilling, road planing,auguring and other applications. The surface is broken and fractured bythe impact of the rotatable cutting tool. Considerable amounts of debrismay be generated and may comprise a large pieces, as well as very fineparticles.

A flange or an extended region of the body of the rotatable cutting tooladjacent of the bore of the holder has been employed to minimise debrisfrom building up between the holder and the rotatable cutting tool.

We have now found a rotatable cutting tool that provides improvedrotational performance and reduces the likelihood of uneven wear andpremature destruction. The rotatable cutting tool of the presentinvention provides both a rotational moment on impact and cuttingthrough the debris as well as provides protection for the block toprevent infiltration of debris.

SUMMARY OF THE INVENTION

In one form of the present invention there is provided a rotatablecutting tool comprising a shank for locating the rotatable cutting toolon a work face, a body and a hard tip wherein said body is of agenerally tapered shape and comprises at least one flight wherein saidat least one flight extends longitudinally and at least partially aroundthe body whereby movement of the rotatable cutting tool through asubstrate urges the tool to rotate.

The flight or flights extending from the body of the rotatable cuttingtool present an oblique surface to a substrate through which the cuttingtool passes. The forward movement of the cutting tool through thesubstrate causes the substrate to bear upon the oblique surface suchthat a rotational moment is applied to the cutting tool urging it torotate.

The at least one flight extending from the body of the rotatable cuttingtool extends longitudinally and at least partially around the body. Itwill be understood that by the term “at least partially around” it ismeant a variety of configurations whereby the flight or flights extendin a generally longitudinal direction but include a lateral offset. Forexample, the flight or flights may extend transversely from the body ofthe rotatable cutting tool. In a preferred configurations, the flight orflights may extend in a spiral or helix from the body of the rotatablecutting tool. It will be appreciated that there are many similarconfigurations that may be employed to provide a flight that extendslongitudinally and partially around the body of the rotatable cuttingtool.

The at least one flight extending from the body of the rotatable cuttingtool may be of constant dimension. Preferably, the flight or flights mayincrease in dimension as the flight or flights extend away from the tipof the rotatable cutting tool. Preferably the oblique surface providedto the direction of travel of the rotatable cutting tool increases insize as the flight or flights extend away from the tip. In order toprovide sufficient strength in the flight or flights, the flight orflights may increase in breadth as they extend away from the tip.

The rotatable cutting tool of the present invention comprises a shank.The shank extends from the rear of the body and is preferably of agenerally cylindrical form such that it can be rotate in the insertedinto a bore. The shank preferably includes a locating means for locatingthe rotatable cutting tool at a desired depth within the bore. Thelocating means may be of any convenient configurations, but ispreferably in the form of a circumferential channel or slot.

The work face may include suitable bores. Preferably, the work face hasa plurality of blocks mounted on the work face, which blocks includesuitable bores. By using blocks, it is generally easier to remove therotatable cutting tools for replacement. Typically, the blocks may beconfigured to allow easy access to the rear of the block where aretaining means is generally used to hold of the rotatable cutting toolswithin the bores.

Insertion of the rotatable cutting tool into a block may expose the rearof the shank, including the locating means through the rear of theblocks. A retaining clip or a retaining ring may be received in acircumferential channel and may bear upon a boss disposed on the rear ofthe block. Removal of the retaining ring or clip allows for the easyremoval of the rotatable cutting tool from the block. The rear of theblock may preferably provided in an accessible location on the worksurface.

The body of the rotatable cutting tool is of a generally tapered form.It will be appreciated that by “generally tapered form” is meant thatthe cross-section of the body generally increases in size from the tipof the rotatable cutting tool to the point at which the body undergoesthe transition to the shank. The transition from the body to the shankmay be a stepwise transition or a tapered transition or a combinationthereof. The generally tapered form of the body may be a continuoustaper whereby the increase in cross-sectional dimension of the body isconstant from the tip to the shank. Alternatively, the taper may be avariable taper whereby the increase in cross-sectional dimension of thebody can vary from the tip to the shank. The taper may also be a steppedtaper that includes a number of stepped increases in cross-sectionalarea from the tip to the taper.

The body may have a circular cross-section extending along its length ormay have a polygonal cross-section or a combination thereof.

The tip of the rotatable cutting tool is preferably multifaceted, suchas in the form of a triangular or square pyramid. The tip is preferablyformed from a cemented carbide or other wear resistant material. Thehard tip is generally formed separately from the shank and body of therotatable cutting tool and inserted into a recess at the leading end ofthe body. The hard tip may be retained in the body of the rotatablecutting tool by frictional engagement or is preferably brazed into thebody.

In a preferred embodiment of the present invention in the rotatablecutting tool includes a hard tip in the form of a pyramid. The body ofthe rotatable cutting tool adjacent to the tip has a polygonalcross-section such that each apex of the cross-section of the body isgenerally aligned with an edge of the tip. Thus a face of the tip meetswith a corresponding face on the body. The face on the body may beinclined at the same angle as the face of the tip or inclined at adifferent angle, preferably a lesser angle such that removal of debriscreated by the impact of the rotatable cutting tool is not impeded.

In this embodiment, it is preferred that the flights extend from theleading edge of the body at each apex of the cross-section of the bodyand sweep across the face of the body as they extend longitudinally.Desirably each flight is oriented and dimensioned to correspond to theother flights. As the tapered body extends from the tip, the increase inthe cross-sectional dimensional may become greater and the cross-sectionof the body may transform to a circular cross-section.

Rotatable cutting tools are generally mounted on a work face byinsertion of the shank into a bore such that the cutting tools are ableto relatively freely rotate as a result of the impact of the cuttingtool. We have found that the rotatable cutting tool of the presentinvention provides an improved free rotation within a bore. It isbelieved, without wishing to be bound by theory, without by providingflights that extend longitudinally and at least partially around thebody of the rotatable cutting tool an increased rotational moment isgenerated as the rotational cutting tool passes through either thedebris from a cut surface or the surface itself. In addition, it isbelieved, again without wishing to be bound by theory, that the flightsassist in distributing the debris away from the bore and shank, therebydecreasing the likelihood of the rotation of the cutting tool beingimpaired.

The rotatable cutting tools of the present invention may be used in avariety of applications including mining, ditching, trenching, drilling,road planing, auguring and other applications. The cutting tools may beattached to a driven member such as, for example, a chain, a wheel, or adrum.

The present invention will now be described with reference to theaccompanying drawings that serve to illustrate the invention and notlimit its scope.

FIG. 1 shows a side view of a rotatable cutting tool according to oneembodiment of the present invention.

FIG. 2 shows a side view of the cutting tool of FIG. 1 rotated about itslongitudinal axis.

FIG. 3 shows a perspective view of the rotatable cutting tool shown inFIG. 1.

FIG. 4 shows an end view of the rotatable cutting tool shown in FIG. 1.

FIG. 5 shows a side view of a rotatable cutting tool according to asecond embodiment of the invention.

FIG. 6 shows a side view of the rotatable cutting tool shown in FIG. 1rotated about its longitudinal axis.

FIG. 7 shows a perspective view of the rotatable cutting tool shown inFIG. 5.

FIG. 8 shows an end view of a rotatable cutting tool shown in FIG. 5.

FIGS. 1 to 4 show a rotatable cutting tool according to one embodimentof the present invention. The rotatable cutting tool 1 having a shaft 2,a body 3 and a tip 4. The shaft 2 includes a circumferential channel 5for receiving a retaining ring or retaining clip (not shown) to retainthe rotatable cutting tool 1 in a holder (not shown) on the workface(not shown) of an implement. The tail end of the shaft is provided witha chamfered surface 6 for easy insertion of the shaft 2 into the bore(not shown) of a block (not shown).

The shaft 2, at its leading end has a collar 7 for engagement with theopening of the bore (not shown). The collar 7 assist in keeping debrisfrom entering into the bore.

The tip 4 of the portable cutting tool 1 is formed from a cementedcarbide. The tip 4 is in the shape of a triangular pyramid. The tip 4has three wear faces 8.

The body 3 is in the form of a truncated triangular pyramid with therespective faces at a lesser angle to the direction of travel of therotatable cutting tool 1. In this way, the faces 9 of the body 2 do notrestrict the removal of debris created by the impact of the tip 4 on thesurface to be removed.

The respective faces 9 on the body 3 form a shoulder 10 that engages thefront end of the block (not shown).

The body 3 includes flights 11 that extend along the length of the body3. The flights 11 initiate from the apex of the body 3 where it meetsthe tip 4 and radiate from the body 3. The flights extend away from thetip in a clockwise orientation to provide oblique surfaces 12 forpushing against debris and causing the rotatable cutting tool 1 torotate in an anticlockwise direction. Between the oblique surfaces 12are channels 13 through which some of the debris may pass. The flights11 increase in size as they extend along the body 3 having greatertrailing portions 14 to provide greater support for the leading surfaces12 as they are subjected to greater force from the debris.

The flights 11 extend in a generally spiral form longitudinally alongthe body 3 of the rotatable cutting tool 1 and partially around therotatable cutting tool 1.

FIGS. 5 to 8 show a second embodiment of the present invention in theform of a rotatable cutting tool 21 having a shaft 22, a body 23 and atip 24. The shaft 22 and the tip 24 are in the same form as therespective shaft 2 and tip 4 from FIGS. 1 to 4. The body 23 of therotatable cutting tool 21 is of a compound form having a leading portion35 in the form of a truncated pyramid and a trailing portion 36 in theform of a truncated cone. An intermediate portion 37 provides for thetransition between the leading portion 35 and the trailing portion 36.

Flights 31 extend from the apex of the leading portion 35, adjacent thetip 24 along the length of the body and in a clockwise directionpartially around the body 23. The flights 31 have oblique surfaces 32that increase in size as they extend along the length of the body 23.

We have found that providing a compound body form in the rotatablecutting tool we are able to provide a greater surface on the face radialto the axis of the tool. By transforming the cross-section of the bodyfrom a polygon to a circle and increasing its radius, better protectionis provided to the bore in which the shank of the tool is mounted. Thisallows the flights to extend further from the axis of the tool, therebyincreasing the rotational moment exerted by the passage of debris acrossthe flights.

It will be appreciated by those skilled in the art that variations andmodifications to the invention described here and will be apparentwithout departing from the spirit and scope thereof. The variations andmodifications as would be apparent to persons skilled in the art aredeemed to fall within the broad scope and ambit of the invention asherein set forth.

1. A rotatable cutting tool comprising a shank for locating therotatable cutting tool on a work face, a body and a hard tip whereinsaid body is of a generally tapered shape and comprises at least oneflight wherein said at least one flight extends longitudinally and atleast partially around the body whereby movement of the rotatablecutting tool through a substrate urges the tool to rotate.
 2. Therotatable cutting tool according to claim 1 wherein the at least oneflight increase in dimension as the at least one flight extend away fromthe tip of the rotatable cutting tool.
 3. The rotatable cutting toolaccording to claim 1 wherein the oblique surface provided to thedirection of travel of the rotatable cutting tool increases in size asthe flight or flights extend away from the tip.
 4. The rotatable cuttingtool according to claim 1 wherein a shank extends from the rear of thebody and is of a generally cylindrical form whereby it is rotatable wheninserted into a bore.
 5. The rotatable cutting tool according to claim 1wherein the shank includes a locating means for locating the rotatablecutting tool at a desired depth within the bore.
 6. The rotatablecutting tool according to claim 1 wherein the generally tapered form ofthe body is a continuous taper whereby the increase in cross-sectionaldimension of the body is constant from the tip of the shank.
 7. Therotatable cutting tool according to claim 1 wherein the taper is avariable taper whereby the increase in cross-sectional dimension of thebody varies from the tip to the shank.
 8. The rotatable cutting toolaccording to claim 7 wherein the taper is a stepped taper that includesstepped increases in cross-sectional area from the tip to the taper. 9.The rotatable cutting tool according to claim 1 wherein the body has acircular cross-section extending along its length.
 10. The rotatablecutting tool according to claim 1 wherein the body has a polygonalcross-section extending along its length.
 11. The rotatable cutting toolaccording to claim 1 wherein the body has a cross-section that includesboth circular and polygonal sections.
 12. The rotatable cutting toolaccording to claim 1 wherein the tip of the rotatable cutting tool ismultifaceted.
 13. The rotatable cutting tool according to claim 12wherein the tip is a square pyramid or a triangle pyramid.
 14. Therotatable cutting tool according to claim 1 wherein the tip is formedfrom a cemented carbide or other wear resistant material.
 15. Therotatable cutting tool according to claim 1 wherein the hard tip isformed separately from the shank and body of the rotatable cutting tooland inserted into a recess at the leading end of the body.
 16. Therotatable cutting tool according to claim 1 wherein the rotatablecutting tool includes a hard tip in the form of a pyramid, the body ofthe rotatable cutting tool adjacent to the tip has a polygonalcross-section whereby each apex of the cross-section of the body isgenerally aligned with an edge of the tip and each face of the tip meetswith a corresponding face on the body, and wherein the face on the bodyis inclined at a lesser angle whereby removal of debris created by theimpact of the rotatable cutting tool is not impeded.